The role of membrane potential in transduction of hormonal messages will be investigated in isolated rat adipocytes. The lipolytic effect of catecholamines and the anti-lipolytic effect of insulin will be compared under circumstances of altered ionic environment, resting membrane potential and hormonal stimulation. Membrane potential will be measured with radioactive and fluorescent membrane potential sensitive probes. Adrenergic blockers will be employed to characterize the response to catecholamines. Parallel studies will be perfomred with cyclic nucleotides and the effect of insulin and catecholamines on cyclic nucleotide generation. These studies will determine the role of an electric potential and specific ions to the biological response to hormones. This information will contribute to an understanding of the disordered metabolism in diabetes mellitus and possibly lead to improvement in the therapy of this disease. Since membrane potential and stimulated ion transport are important for replication, these studies will suggest an investigative approach to the disordered control of neoplasms by cell surface active regulators such as hormones.